|Publication number||US4875405 A|
|Application number||US 07/073,592|
|Publication date||Oct 24, 1989|
|Filing date||Jul 15, 1987|
|Priority date||Jul 16, 1986|
|Also published as||DE3623928A1, EP0253086A2, EP0253086A3, EP0253086B1|
|Publication number||07073592, 073592, US 4875405 A, US 4875405A, US-A-4875405, US4875405 A, US4875405A|
|Inventors||Bruno Bernhardt, Heinrich Kedzierski|
|Original Assignee||Wabco Westinghouse Steuerungstechnik Gmbh|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (41), Referenced by (5), Classifications (17), Legal Events (4)|
|External Links: USPTO, USPTO Assignment, Espacenet|
The present invention relates, in general, to sealing devices and, more particularly, the invention relates to an apparatus for sealing two machine components, at least one of such two machine components being movable relative to the other, such as, the piston of a working cylinder.
Prior to the present invention, sealing devices of this kind, which are useful in sealing the piston of a working cylinder, have been disclosed in the art. See, for example, German Pat. No. DE 33 15 050 A1. This particular sealing device makes use of the excellent sliding and sealing properties of the PTFE plastic material, more commonly known as Teflon, for the sealing element. However, since this material, when used as the sealing element, is not sufficiently elastic, an elastic O-ring, installed in a groove of the piston, is used as an elastic support element to generate the necessary elastic pressure force for the sealing element and to ensure a sufficient seal. The sealing element in this prior art cylinder is constructed as a sleeve-shaped ring which rests directly on the elastic support. The center section of the sealing element is slightly bulged due to the pressure force of the support which is directed outward unto the sliding surface of the cylinder and functions as the sealing force so that a contact surface results. The dimensions of the contact surface remain undefined. An additional disadvantage of this device, known to the art, resides in the fact that the support must have some clearance in an axial direction within the groove holding it to allow for the change in the volume of the support as necessary for generating the elastic sealing force. A clearing of this kind, however, also signifies that the axial position of the support is not defined, or that the support acquires an undesirable axial mobility within the groove which hinders the exact positioning of the piston.
The disadvantages mentioned above, in relation to the device known to the art, can be avoided if a different sealing principle is applied, such as known from German Pat. No. DE 24 58 974 A1. In this device, known to the art, the piston in a working cylinder is encircled and sealed by a rubber cup packing. The packing of this seal, known to the art, advantageously forms two sealing edges which, due to their elastic material and the prestress resulting from it, are pressed against the sliding surface of the working cylinder. It is conceivable to coat this seal, known to the art, with a layer of PTFE plastic or a similar material with excellent sliding properties. However, a solution of this kind would cause design and production problems without assuring a sufficiently high elastic pressure force for the sealing edges.
The present invention teaches a sealing apparatus for sealing two machine components which can slide against one another. One of these components has a sliding surface along which the other component slides with a sealing element attached to it. The sealing element consists of a plastic material having low-friction and relatively low elasticity, such as PTFE. A support is provided for attaching at least a portion of the sealing element, which slides along the sliding surface of the other component, and to provide a requisite amount of support for the sealing element. The support is constructed in such a manner that it will exhibit elasticity in a plane vertical to or more or less vertical to the sliding surface. The portion of the sealing element which slides along the sliding surface is constructed in such a way that it encircles the support in a direction of the sliding motion. Mounting protrusions of the sealing element, which extend in a plane vertical to or more or less vertical to the sliding surface, rest against corresponding support surfaces of the support which are also oriented in a plane vertical to or more or less vertical to the sliding surface. When the sealing element and the support are not mounted the outer distance of the support surfaces, measured in a direction of the sliding motion, is greater than the distance between the mounting protrusions of the sealing element. The portion of the sealing element which slides along the sliding surface is constructed such that it tries, under the influence of the prestress exerted by the support surfaces on the mounting protrusions, to bend upward toward the sliding surface at least in the area of such mounting protrusions.
It is, therefore, one of the primary objects of the present invention to provide a sealing apparatus which can advantageously utilize the properties of an excellent but essentially non-elastic sliding material.
Another object of the present invention is to provide a sealing apparatus in which a prestress exerted on the sealing element by a support, when installed and mounted, will cause a pressure force directed toward the sliding surface for the portion of the sealing element in sliding engagement with the sliding surface thereby generating a maximum sealing force at the free ends of the sealing element while the sealing force gradually diminishes in the center of the sealing element so that a sufficiently definable sealing edge is also obtained.
Still another object of the present invention is to provide a sealing apparatus which can control and seal a relatively long sealing edge on a flat or wavy sealing surface.
Yet another object of the present invention is to provide a sealing apparatus which can be used as a single-lip sealing element as well as a double-lip sealing element.
These and various other objects and advantages of the sealing apparatus of the present invention will become more readily apparent to those persons who are skilled in the sealing art from the following more detailed description when such description is taken in conjunction with the attached drawings and with the appended claims.
FIG. 1 is a fragmented cross-sectional view of one presently preferred embodiment of the sealing apparatus constructed according to the present invention; and
FIG. 2 is a fragmented cross-sectional view of an alternative embodiment of a sealing apparatus constructed according to the present invention.
In each of the views, illustrating the sealing apparatus of the present invention, identical numerals have been used to designate identical elements of the invention.
Although the invention is not limited thereto, it will, for the purposes of illustration only, be described as it relates to a working cylinder for which the invention has excellent utility.
Now refer more particularly to FIG. 1, which shows a section of a working cylinder containing a sealed piston to which pressurized air can be applied. As illustrated therein, a cylinder tube 8 has in its interior a sliding surface 9 for the piston which is attached to a piston rod 14. The piston consists of a rigid mount 17, for example, of metal, a support 5 attached on top of the mount 17, and a sealing element 2.
The mount 17 is pushed unto the tapered end 16 of the piston rod 14 in such a way that it rests against the shoulder 15 of the piston rod 14. A nut 19 for securing and attaching the mount 17 is screwed unto a thread 20 at the end of the piston rod 14. A spring washer 18 is inserted between the nut 19 and the mount 17. In a manner not shown by the drawing, the mount 17 is so attached that it cannot be turned in relation to the piston rod 14. Furthermore, the mount 17 is attached to the piston rod 14 and sealed, which is not shown in the drawing. A sealing ring placed between the mount 17 and the piston rod 14, for example, may be used for this purpose.
The mount 17 is constructed as a perforated disk and is thinner in the area of the outer rim than in the center. The outer rim area 3 carries the support 5, which consists of rubber or a similarly elastic material. The support 5, is equipped with two ring-shaped protrusions 13 and 21 which are pointing inward and with which the support 5 encircles the outer rim area 3 of the mount 17. The support 5 is attached to the mount 17 in a way not shown by the drawing (for example, by adhesive). Furthermore, the support 5 is equipped with two sleeve-shaped protrusions 12 and 22 which extend more or less into the direction of the sliding motion.
The support 5, described above, is encircled in the direction of the sliding motion by the sealing element 2 which has a U-shaped cross-section in the sliding direction and vertical to the sliding surface 9, i.e., in the plane of FIG. 1. The two sides of the U are formed by the two ring-shaped inward-pointing protrusions 10 and 24 of the sealing element 2. The inner surfaces of the two protrusions 10 and 24 of the sealing element 2, which extend in a plane vertical to or more or less vertical to the sliding surface 9, rest against the outer end surfaces of the support's 5 protrusions 12 and 22 which thus serve as support surfaces 11 and 23.
The sealing element 2 consists of a material having very low friction, such as PTFE plastic material, which however, is also of relatively low elasticity. In order to obtain a sufficiently strong seal between the piston and the sliding surface, even after prolonged operation and possibly showing wear, the sealing element 2 has to be pressed against the sliding surface 9 under the effect of elastic prestress. The material of the sealing element 2 alone cannot generate this prestress (elasticity) or cannot generate it in sufficient strength. For this reason, the sealing element 2 is supported by the elastically-constructed support 5. The two protrusions 12 and 22 of the support 5 are constructed and proportioned in such a way that they exert a predetermined elastic prestress force on the end areas of the sealing element 2. In addition to this prestress force, generated by the elasticity of the support 5 which works in a plane vertical to or more or less vertical to the sliding surface 9, the sealing device shown makes it possible to generate an additional component of prestress force which works in the direction of the sliding surface 9 with the aid of the following measures.
The outer distance of the support surfaces 11 and 23 has been proportioned in such a way that when the sealing element 2 and the support 5 are not mounted it is slightly greater than the inner distance between the protrusions 10 and 24 of the sealing element 2. This means that the sealing element 2 has to be clamped unto the support 5 when the device described is being assembled. After assembly, therefore, the protrusions 12 and 22 of the support 5, with the aid of the support surfaces 11 and 23, exert a force on the protrusions 10 and 24 of the sealing element 2 which force is more or less oriented in the direction of the sliding motion and would, in the absence of the support function of the sliding surface 9, cause the ends 7 and 1 of the sealing element 2 to be widened or bent out, respectively.
When the piston is mounted in the cylinder the sealing element 2 rests against the sliding surface 9 in such a way that the sealing element 2 cannot be widened. Nevertheless, the sealing element 2 remains under the effect of a corresponding prestress which tries to widen or bend the sealing element 2 outward in the area of the protrusions 10 and 24 or in the end areas 1 and 7 while the forces of the protrusions 12 and 22 are applied to the protrusions 10 and 24 in the manner of levers. This means that in addition to the normal elastic pressure force which is addition to the normal elastic pressure force which is exerted on the sealing element 2 by the protrusions 12 and 22 an additional pressure force results from the "widening effect" described above. The result is a pressure force exerted on the sealing element 2 in a direction of the sliding surface 9 that functions as a sealing force which reaches a maximum in the end areas 1 and 7 of the sealing element 2 and steadily decreases toward the center 4 of the sealing element 2. In this manner, the center section of the support 5, as seen in the direction of the sliding motion, does not exert any or at least not any significant pressure force on the sealing element 2.
The space 6 existing in the central area of the piston construction, described above, between the ends 1 and 7 of the sealing element 2, which function as sealing edges, for example, can be bled in a way not shown, in order to produce a pressure gradient between the chambers of the working cylinder to which pressurized air can be applied and the above-named central area of the piston.
Now refer to FIG. 2, which shows a refinement of the device represented in FIG. 1, for example, for application in hydraulic systems. In addition to the components of the device represented in FIG. 1, the sealing device, according to FIG. 2, has two rigid support elements 28 and 29, for example, made of metal. These support elements 28 and 29 are attached on the piston rod 14 or to the piston by pushing them unto the tapered end 16 of the piston rod 14, like the mount 17, and by placing them on both sides of the mount 17.
The support elements 28 and 29 are attached to the mount 17 by not specifically defined means of attachment in such a way that the protrusions 13 and 21 of the support 5 are located between the support elements 28 and 29 and the mount 17 and on the corresponding contour of the support elements 28 and 29.
Each support element 28 and 29 is equipped with a sleeve-shaped support protrusion 26 and 30 which extends outward and more or less in the direction of the sliding motion or parallel to the protrusions 12 and 22 of the support 5. With the aid of these support protrusions 26 and 30 the support elements 28 and 29 support the protrusions 12 and 22 of the support 5; an elastic support or cushioning part 25, constructed as an O-ring, is inserted between the support protrusion 26 and the protrusion 12 of the support 5; and another elastic support or cushioning part 31, also constructed as an O-ring, is inserted between the support protrusion 30 and the protrusion 22 of the support 5. The contours of the protrusions 12 and 22 of the support 5 are adapted to the shape of the support parts 25 and 31 in order to assure an efficient transfer of the support forces. The support parts 25 and 31 are mounted in such a way that they support the outer end areas of the protrusions 12 and 22 of the support 5 under the effect of a predetermined prestress.
The sealing element 2 is equipped with two radial bores 32 and 33 which serve the purpose of connecting the spaces 6 between the sealing element 2 and the support 5 with the space contained between the sealing element 2 and the cylinder tube 8 and for bleeding the latter. This facilitates the formation of the differential pressure required for blocking the piston.
The device described up to now, according to FIG. 2, can be used to increase still further the pressure forces exerted on the sealing element 2 in the area of the sealing edges 1 and 7 of the sealing element 2 in order to make it possible to apply the device even with very high pressures, as those occurring in hydraulic systems, for example.
While two embodiments of the present invention have been described in detail above, it should be understood by those persons who are skilled in the sealing art that other adaptations and modifications can be made without departing from the spirit and scope of the attached claims.
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|FR2379971A7 *||Title not available|
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|Citing Patent||Filing date||Publication date||Applicant||Title|
|US4930791 *||Oct 2, 1989||Jun 5, 1990||Fmc Corporation||Plastic bore seal|
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|US6135008 *||Mar 16, 1998||Oct 24, 2000||Haldex Brake Corporation||Piston with lubricant-scraping ring and lubricant return ports|
|US6863277 *||Sep 27, 2002||Mar 8, 2005||Zf Sachs Ag||Piston ring for the piston of a vibration damper|
|U.S. Classification||92/194, 277/449, 92/255, 277/910, 92/201, 92/240, 92/258, 277/468|
|International Classification||F16J1/02, F16J15/32, F16J15/16|
|Cooperative Classification||Y10S277/91, F16J15/3232, F05C2225/04, F16J15/3208|
|European Classification||F16J15/32B2, F16J15/32B7|
|Aug 20, 1987||AS||Assignment|
Owner name: WABCO WESTINGHOUSE STEUERUNGSTECHNIK GMBH & CO., H
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNORS:BERNHARDT, BRUNO;KEDZIERSKI, HEINRICH;REEL/FRAME:004810/0539
Effective date: 19870708
|May 25, 1993||REMI||Maintenance fee reminder mailed|
|Oct 24, 1993||LAPS||Lapse for failure to pay maintenance fees|
|Jan 4, 1994||FP||Expired due to failure to pay maintenance fee|
Effective date: 19931024